The United States and France stepped up their calls on Thursday for Yemen President Ali Abdullah Saleh to step down, after overnight gunbattles killed dozens of people.   

US Secretary of State Hillary Clinton, speaking in Paris, urged all sides to immediately cease violence, and a French foreign ministry spokesman told reporters at a G8 summit that France blamed the latest bloodshed on Saleh's refusal to sign a transition deal.

The mounting threat of civil war will put the crisis in Yemen high on the agenda of Group of Eight talks in the northern French seaside town of Deauville, with world leaders keen to get the matter discussed by the UN Security Council as quickly as possible, a European diplomat told Reuters.

"We call on all sides, on all sides, to immediately cease the violence," Clinton told a news conference in Paris. "We continue to support a united and stable Yemen and we continue to support the departure of President Saleh who has consistently agreed that he would be stepping down from power and then consistently reneged on those agreements," she said.

More than 40 people have been killed since Monday in violence that threatens to spread into other areas of Sanaa.

The most recent clashes have been concentrated in a part of northern Sanaa where fighters loyal to powerful tribal leader Sadiq al-Ahmar have been trying to take over government buildings including the interior ministry.    

The French foreign ministry spokesman said the only choice left open to Saleh was to sign a government transition deal mediated by Gulf neighbours.   

"We deplore the fighting that occurred overnight which was a direct result of the current political impasse, for which President Saleh has direct responsibility due to his refusal to sign the GCC transition agreement," he said, referring to the Gulf Cooperation Council.

In Deauville, Japanese foreign ministry spokesman Satoru Satoh also urged Saleh to sign a power transition deal and said it was "extremely regrettable" that so many people had died.

"Japan strongly hopes that President Saleh will follow through on his commitments to peacefully transfer power, and that the parties concerned will reach a consensus, leading to the early stabilization of the situation," he said. - Reuters